1. Field of the Invention
The present invention relates to an automatic leveling apparatus and method of a headlamp of a vehicle for automatically controlling to incline an optical axis of a headlamp, based on an inclination in a front and rear direction of a vehicle (hereinafter, referred to as pitch angle), in a direction of canceling an amount in correspondence with the pitch angle (hereinafter, referred to as auto leveling). Particularly, the present invention relates to an automatic leveling apparatus for controlling to incline an optical axis of a headlamp in an up and down direction by calculating the pitch angle based on a control constant inherent to the vehicle.
2. Description of the Related Art
In a headlamp used in an automatic leveling apparatus, for example, a reflector inserted with a light source is supported by a lamp body inclinably around a horizontal inclination axis and an optical axis of the reflector (headlamp) can be inclined around the horizontal inclination axis by an actuator.
Further, an automatic leveling apparatus of a related art comprises a vehicle height sensor for detecting a change in a height of an axle portion of a front wheel or a rear wheel of a vehicle, a vehicle speed sensor for detecting a speed of the vehicle, a controller for controlling to drive an actuator based on respective detecting signals of the vehicle height sensor and the vehicle speed sensor at the vehicle. The automatic leveling apparatus of the related art controls an optical axis of a headlamp (reflector) to be brought into a state of being always constant relative to a road face.
That is, when a direction of the optical axis of the headlamp is directed upward by an inclination of a vehicle body, glare is cast to a vehicle running on an opposite lane, or when the direction of the optical axis of the headlamp is directed downward, remote recognizability of a driver is deteriorated. Therefore, the direction of the optical axis of the headlamp is controlled to be always constant.
Meanwhile, in controlling to drive the actuator based on the pitch angle, it is necessary to calculate the pitch angle in consideration of the specification of the vehicle. That is, depending on a kind of the vehicle, the vehicle comprises one vehicle height sensor or two vehicle height sensors, further, depending on the kind of the vehicle, a length of a wheel base differs. Therefore, a control constant coinciding with the specification of the vehicle is set in correspondence with the kind of the vehicle, the set control constant is written to a memory of ECU (Electronic Control Unit) and ECU is made to be common regardless of the kind of the vehicle (refer to JP-A-2001-328484 (refer to page 2 through page 4, FIG. 1, FIG. 5)).
ECU of the related art is made to be common regardless of the specification of the vehicle by writing the control constant inherent to the vehicle to the memory of ECU after integrating the headlamp to the vehicle. However, in controlling to drive the actuator, it is not determined whether the control constant is written to the memory. Therefore, when the control constant of the memory is erroneously written, or a wrong control constant is written to the memory, accurate auto leveling cannot be carried out.